The term "flapper" primarily refers to a young woman in the 1920s who behaved and dressed in a boldly unconventional manner. Flappers were known for wearing short dresses (around knee-length), bobbed hair, and embracing freedom from traditional societal constraints. They often wore sleeveless, low-cut dresses, used bold cosmetics, and accessorized with headbands, cloche hats, bangle bracelets, and long strands of beads. Flappers engaged in activities that were considered unladylike at the time, such as smoking, drinking in public, attending social events without chaperones, and being open about sexual activity. This lifestyle was a symbol of the cultural and social liberation during the Roaring Twenties, especially in the United States after World War I. The word "flapper" was used to describe this new modern woman who pushed social boundaries and embraced independence and freedom.
Additionally, "flapper" can also mean a young bird just learning to fly or more generally something broad and flat used for striking or making noise by striking, but the social and cultural meaning related to the 1920s young women is the most recognized usage.